pgsql: pgcrypto: Remove static storage class from variables

pgcrypto: Remove static storage class from variables

Variables p, sp and ep were labeled with static storage class
but are all assigned before use so they cannot carry any data
across calls. Fix by removing the static label.

Also while in there, make the magic variable const as it will
never change.

Author: Japin Li <japinli(at)hotmail(dot)com>
Reviewed-by: Daniel Gustafsson <daniel(at)yesql(dot)se>
Reviewed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Discussion: https://postgr.es/m/ME0P300MB0445096B67ACE8CE25772F00B6F72@ME0P300MB0445.AUSP300.PROD.OUTLOOK.COM

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/affd38e55a3cabbc4c64198dde71c22a94877690

Modified Files
--------------
contrib/pgcrypto/crypt-md5.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)